Vertically-storing dock leveler apparatus and method

ABSTRACT

A dock leveler for bridging the gap between a loading dock and the bed of a vehicle parked at the loading dock. The dock leveler is configured for installation on the top of the dock and is designed to rotate from a vertically-stored raised position to at least one lowered, operative position. In some embodiments, the dock leveler can be lowered either for normal operation so that the deck assembly rests on the bed of the vehicle or it can be lowered to accommodate an end-loading condition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to, and is a divisional application of,U.S. patent application Ser. No. 10/854,236, entitled“Vertically-Storing Dock Leveler Apparatus and Method” filed May 27,2004 now U.S. Pat. No. 7,043,790, which is a continuation-in-part, ofU.S. Patent applications entitled, “Vertically-Storing Dock LevelerApparatus and Method” and “Spring Counterbalance Method and Apparatusfor Variably Biasing a Dock Leveler,” filed May 27, 2003, and Sep. 22,2003, respectively, having Ser. Nos. 10/444,971 (now U.S. Pat. No.6,951,041) and 10/664,971 respectively, 10/664,971 now U.S. Pat. No.7,017,220. The disclosures of all three applications: Ser. Nos.10/854,236; 10/444,971; and 10/664,971 are hereby incorporated byreference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to dock levelers. Moreparticularly the present invention relates to vertically-storing docklevelers. The present invention also relates to dock levelers that donot require a pit for installation.

BACKGROUND OF THE INVENTION

Dock levelers are used at loading docks to bridge the gap between aloading dock and the bed of a vehicle parked at the loading dock tofacilitate the loading or unloading of the vehicle. For example, docklevelers enable material handling equipment, such as a fork truck, tomove between the dock and the vehicle bed.

Installation of dock levelers generally falls into two categories:pit-style dock levelers and edge-of-dock levelers. Pit-style docklevelers are installed in a pit or cavity below the level of the dockfloor so that the top of the dock leveler is at dock level when stored.Pit-style dock levelers are typically configured to store horizontally,but some pit-style dock levelers store vertically. Examples of pit-styledock levelers are described in U.S. Pat. Nos. 4,068,338 and 4,928,340.Examples of vertical-storing dock levelers are found in U.S. Pat. Nos.4,825,493 and 5,001,799. Pit-style dock levelers generally have theability to service transport vehicles up to twelve inches above or belowdock level. These dock levelers are typically activated by hydraulic,pneumatic, or mechanical spring systems. Pit-style dock levelers can beexpensive to install due to the expense of the pit. Pit-style docklevelers, particularly horizontally-storing pit-style dock levelers, canalso have the drawback of being more difficult to ensure security andenvironmental control.

Edge-of-dock levelers are attached to the dock wall and therefore do notrequire a pit or shelf for installation. Examples of edge-of-docklevelers can be found in U.S. Pat. Nos. 4,665,579 and 4,689,846.Edge-of-dock levelers are typically smaller and of simpler constructionthan pit-style dock levelers. A drawback of edge-of-dock levelers isthat they can have limited range above and below dock and steeper gradesdue to their relatively short lengths for fork trucks traveling overthem.

A third type of dock installation that is known, but not widely used, isthe horizontally-storing top-of-dock leveler. It is typically similar inconstruction to a horizontally-storing pit-style dock leveler butmounted on top of the dock without a pit. Top-of-dock levelers generallyhave limited below dock range and are generally used to service standardheight trucks from a low dock. Also, top-of-dock levelers are generallyused on an indoor dock, otherwise it requires that the door be modifiedto close properly.

Accordingly, it is desirable to provide a method and apparatus forbridging the gap between a dock and the end of a vehicle bed that can beinstalled economically such as with an edge-of-dock leveler, but whichhas greater vertical range and less steep grades than edge-of-docklevelers. It is also to desirable that the method and apparatus providethe security and environmental control of a vertically-storing dockleveler.

U.S. Pat. No. 3,411,168 is an example of a mechanically-operated,vertically-storing dock leveler. The illustrated dock leveler includes aspring counterbalance to assist in operation. The spring counterbalancemechanism includes a spring, a roller, a cam and an arm. The springcounterbalance tends to urge the dock leveler into the stored, verticalposition. During operation, as the dock leveler rotates toward anoperative position, the weight moment of the dock leveler overcomes theupward bias of the spring counterbalance and the dock leveler falls intoits operative position.

U.S. Pat. No. 3,460,175 is another example of a mechanically-operated,vertically-storing dock leveler. The illustrated dock leveler includesboth a spring counterbalance and pivotable weight to assist inoperation. The spring counterbalance includes a spring, cam, and camroller. The spring counterbalance upwardly biases the dock leveler,whereas the weight downwardly biases the dock leveler when the weight isrotated into its high moment position. In operation, when the dockleveler is rotated toward the horizontal position, the weight rotatesfrom its low moment position to its high moment position. According tothe specification, when the weight is in the high moment position, themoment about the pivotal connection of the deck assembly to the supportmeans is sufficient to overcome the upward biasing action of the springso that the deck assembly remains in the horizontal position. Tore-store the dock leveler, the weight is rotated from the high momentposition to the low moment position. According to the specification,when the weight is in the low moment position, the force provided by thespring is sufficient to rotate the dock leveler into the stored,vertical position.

A drawback of the above-described dock levelers is that the springcounterbalance upwardly biases the dock leveler throughout the rotationof the dock leveler. Accordingly, rotation of the dock leveler downwardis made more difficult because the motion is against the force of thespring. Another drawback of the above-described dock levelers is thatthey require additional components such as the arm and cam roller.

Accordingly, it is desirable to provide a spring counterbalance methodand apparatus for assisting the operation of a mechanically-operated,vertically-storing dock leveler that can upwardly bias the dock levelerat certain angles of rotation, downwardly bias the dock leveler at otherangles of rotation, and/or neutrally bias the dock leveler at yet otherangles of rotation. It is also desirable to provide a method andapparatus for assisting the operation of a mechanically-operated,vertically-storing dock leveler of desirable simplicity.

There is a risk that the dock leveler may unexpectedly raise if usedwith a transport vehicle that has a bed higher than a given workingrange of a particular dock leveler. As a result some dock levelers mayinadvertently raise to an upwardly biased position and raise above thebed of the transport vehicle. This elevated position of the dock levelerwould be undesirable for loading freight on and off a vehicle.

Another limitation of some dock levelers is that because the dockleveler is downwardly biased throughout the generally horizontal workingrange, it therefore requires great effort to lift it from the horizontalposition.

SUMMARY OF THE INVENTION

The foregoing needs are met, to a great extent, by the presentinvention, wherein in one aspect an apparatus and method for bridgingthe gap between a dock and the end of a vehicle is provided that in someembodiments can be installed economically such as with edge-of-docklevelers, but which has greater range and less steep grades thanedge-of-dock levelers.

In accordance with one embodiment of the present invention, a dockleveler is provided having a vertically-storing deck assembly pivotallyconnected to a base assembly, wherein the base assembly is configured tobe installed on the top surface of a dock. Preferably, the deck assemblycan pivot between the vertically-stored position, and lower, operatingpositions. In some embodiments, the lower, operating positions rangefrom about six inches above dock to about eight inches below dock. Insome embodiments, the deck assembly is pivotally attached to the baseassembly at a moveable pivot axis, such that pivot axis can shift from afirst position in the base assembly near the end of the dock to a secondposition in the base assembly farther from the end of the dock. Shiftingthe pivot axis from the first to the second position effectively reducesthe distance the bridge formed by the deck assembly extends in front ofthe dock face. In some embodiments, the dock leveler also includes a lipassembly pivotally attached to the deck assembly. Pivotal rotation ofthe lip from an extended to a pendant position effectively shortens thelength of the bridge (and thus reduces the distance the bridge extendsin front of the dock face) formed by the deck assembly.

In accordance with another embodiment of the present invention, a dockleveler is provided comprising a base means for securing the dockleveler to a top surface of a dock, a vertically-storing means forbridging the gap between a dock and a vehicle backed against a dock, anda means for pivotally attaching the vertically-storing means to the basemeans. In some embodiments, the dock leveler also includes a means forvarying the length of the bridge formed by the deck assembly. In someembodiments, the length-varying means is a lip assembly pivotallyattached to the vertically-storing bridging means. In some embodiments,the length-varying means is a means for moving the pivotally-attachingmeans from a first position to a second position, wherein the firstposition is closer to the end of the dock than the second position.

In accordance with yet another embodiment of the present invention, amethod for bridging the gap between a dock and a vehicle backed into adock is provided which includes operating a vertically-storing,top-of-dock leveler by moving the top-of-dock leveler between avertically-stored and a lowered operative position.

The foregoing needs are met, to a great extent, by the presentinvention, wherein in one aspect an apparatus is provided that in someembodiments can upwardly bias the dock leveler at certain angles ofrotation, downwardly bias the dock leveler at other angles of rotation,and/or neutrally bias the dock leveler at yet other angles of rotation.

In accordance with one embodiment of the present invention, a dockleveler is provided that includes: a base assembly, a deck assemblyconfigured to rotate from a generally vertical stored position to one ormore lowered supported positions, wherein the deck assembly is pivotallycoupled to the base assembly at a pivot point; and, a counterbalanceassembly comprising: a first anchor point, a second anchor point, atleast one effective anchor point, and a biasing member having a centrallongitudinal axis defining a line of action, wherein the biasing memberis coupled to the deck assembly at the first anchor point and to thebase assembly or dock at the second anchor point and wherein the atleast one effective anchor point has a location along the line ofaction, and which location relative to the pivot point changes as thedeck assembly rotates. According to some embodiments, the biasing memberis a spring. According to some embodiments, the spring is coupled to thesecond anchor point by a flexible member and the base assembly comprisesa cam plate having at least one cam surface shaped to deflect the lineof action as the deck assembly rotates by selectively engaging theflexible member.

In accordance with another embodiment of the present invention, acounterbalance assembly for a mechanically-operated, vertically-storingdock leveler is provided. The counterbalance assembly includes: atension means for counterbalancing the deck assembly of a dock leveler,wherein the tension means has a first end and a second end; a means forfixedly coupling the first end of the tension means to the deck assemblyat a first anchor point; a means for flexibly coupling the second end ofthe tension means to a base assembly of the dock leveler at a secondanchor point, wherein the first anchor point and the second anchor pointdefine a direct line of action; and a camming means configured toselectively engage the means for flexibly coupling such that the tensionmeans is deflected away from the direct line of action when the tensionmeans is incorporated in the dock leveler and the deck assembly rotates.

In accordance with yet another embodiment of the present invention, amethod for counterbalancing a mechanically-operating, vertically-storingdock leveler having a rotating deck assembly attached to a base assemblyat a pivot point is provided. The method includes coupling a spring tothe dock leveler with a flexible attachment device, and providing acamming surface configured to cooperate with the flexible attachmentdevice to deflect the spring away from a direct line of action inresponse to the deck assembly rotation. In some embodiments, the cammingsurface is shaped to cause the spring to deflect toward the pivot pointas the deck assembly rotates downward. “Direct line of action” should beunderstood to mean the straight line defined by the fixed anchor pointsto which the spring is coupled, which may or may not overlap the “lineof action” defined by the central longitudinal axis of the spring.

In accordance with another embodiment of the present invention, a dockleveler is provided. The dock leveler includes: a base assemblymountable to a surface of a dock floor; a deck assembly configured torotate between a generally vertical stored position to one or morelowered operating positions, wherein the deck assembly is pivotallycoupled to said base assembly, a spring counterbalance assemblyoperatively connected to the deck assembly and base assembly, whereinthe spring counter balance assembly causes the deck assembly to bedownwardly biased throughout the generally horizontal working range, andthe deck assembly to be upwardly biased at positions above the workingrange; and a hold down assembly engageable with the springcounterbalance assembly when the deck assembly is in the generallyhorizontal working range, wherein the hold down assembly, when engagedwith the spring counterbalance assembly, causes the deck assembly toremain downwardly biased when it is raised above the working range.

In accordance with another embodiment of the present invention, a dockleveler is provided. The dock leveler includes: a base assemblymountable to a surface of a dock floor; a deck assembly configured torotate between a generally vertical stored position to one or morelowered operating positions, wherein the deck assembly is pivotallycoupled to said base assembly, a spring counterbalance assemblyoperatively connected to the deck assembly and base assembly, whereinthe spring counter balance assembly causes the deck assembly to bedownwardly biased throughout the generally horizontal working range, andthe deck assembly to be upwardly biased at positions above the workingrange; and a lever mechanism configured to raise the deck assemblytoward a generally vertical stored position.

In accordance with another embodiment of the present invention, a dockleveler is provided. The dock leveler comprises: a base assemblymountable to a surface of a dock floor; a deck assembly configured torotate between a generally vertical stored position to one or morelowered operating positions, wherein the deck assembly is pivotallycoupled to said base assembly, means for counterbalancing the deckassembly, wherein the deck assembly is downwardly biased throughout thegenerally horizontal working range; means for moving the deck assemblybetween a raised and lowered position; and means for ratchetingmechanism configured to engage the moving means and the deck assembly atmore than one angle relative to one another, wherein the ratchetingmeans is configured to disengage the lever assembly from the deckassembly when the deck assembly is in the generally horizontal workingrange, and wherein the ratcheting means is configured to engage themoving means with the deck assembly when the deck assembly is rotatedabove the working range.

In accordance with another embodiment of the present invention, a dockleveler is provided. The dock leveler comprises: a base assemblymountable to a surface of a dock floor; a deck assembly configured torotate from a generally vertical stored position to one or more loweredoperating positions, wherein the deck assembly is pivotally coupled tosaid base; a lip pivotally coupled to said deck assembly and configuredto rotate from an extended position generally parallel to the deckassembly to a retracted position generally perpendicular to the deckassembly, and a latch configured to selectively hold the lip in theextended position.

In accordance with another embodiment of the present invention, avertically storing dock leveler is provided. The dock leveler comprises:a support structure mountable to a loading dock; a deck assemblypivotally mounted to the support structure and configured to movebetween a substantially vertical position and a working position; acounterbalance assembly comprising a spring connected to the supportstructure and the deck assembly, the spring having a moveable effectiveanchor point at one end; wherein a line of action of the spring moves asthe effective anchor point moves; and a hold down mechanism selectivelydis-engageable and configured to cause the deck assembly to remaindownwardly biased when it is raised above a working range when the holddown mechanism is engaged.

In accordance with another embodiment of the present invention, a methodof operating a dock leveler where the dock leveler comprises: a supportstructure mountable to a loading dock; a deck assembly pivotally mountedto the support structure and configured to move between a substantiallyvertical position and a working position; a counterbalance assemblycomprising a spring connected to the support structure and the deckassembly, the spring having a moveable effective anchor point at oneend, wherein a line of action of the spring moves as the effectiveanchor point moves; a hold down mechanism selectively dis-engageable andconfigured to cause the deck assembly to be downwardly biased when thedeck assembly is in, or raised above, a working range when the hold downmechanism is engaged; a lifting mechanism configured to permit anoperator to actuate the lifting mechanism and raise the deck assemblyfrom a working range to a stored position; a storage latch mechanism;and a storage latch disengaging mechanism configured to selectivelydisengage the storage latch mechanism. The method comprises: releasingthe storage latch mechanism by activating the storage latch disengagingmechanism; and lowering the deck assembly.

In accordance with another embodiment of the present invention, a lipassembly for a dock leveler is provided. The lip assembly comprises: aframe; a deck assembly pivotally connected to the frame; a lip pivotallyconnected to the deck assembly; a spring connected to the frame at oneend and the deck assembly at the other end, the spring biasing the deckassembly, a lip latch biased to a first position; and a latch barattached to the lip and configured to communicate with the lip latchsuch that lip latch urges the latch bar to remain in a position toresist the lip retracting when the lip near the extended position.

In accordance with another embodiment of the present invention, a lipassembly for pivoting a lip about a deck assembly of a vertical storingdock leveler is provided. The lip assembly comprises: a lip pivotallyconnected to the deck assembly and movable between a pendant positiongenerally perpendicular to the deck assembly and an extended positiongenerally parallel to the deck assembly; a latch link pivotallyconnected to the lip at one end of the latch link and the other end ofthe latch link having at least one engaging surface; a crank armconnected to the latch link at one end of the crank arm and another endof the crank arm is connected to the deck assembly, and biasing meansconfigured to urge the crank arm to urge the latch link to urge the lipto the extended position.

In accordance with another embodiment of the present invention, a methodoperating a dock leveler is provided. The method comprises: inserting alip actuator into a lip actuator receiver; rotating the lip by rotatingthe lip actuator; and lowering a dock leveler from a substantiallyvertical position.

In accordance with another embodiment of the present invention, a dockleveler is provided. The dock leveler comprises: a frame configured tobe mounded to a loading dock; a deck assembly having a top surface, thedeck assembly pivotally mounted to the frame; and a counter balancingspring mounted at one end to the deck assembly and mounted to the frameat the other end, the counter balancing spring having a line of actionlocated substantially above a pivot axis of the deck assembly.

In accordance with another embodiment of the present invention, a dockleveler is provided. The dock leveler comprises: a frame configured tobe mounded to a loading dock; a deck assembly having a top surfacepivotally mounted to the frame; and means for counter balancing the deckassembly mounted at one end to the deck assembly and mounted to theframe at the other end, the counter balancing means locatedsubstantially above the top surface of the deck assembly.

In accordance with another embodiment of the present invention, a methodfor protecting the counter balance mechanism for a dock leveler isprovided. The method comprises: locating a dock leveler deck assemblycounter balance mechanism to one side of a deck assembly; providing atleast one curb along at least one edge of the deck assembly; andhousing, at least in part, the counter balance mechanism with the atleast one curb.

In accordance with another embodiment of the present invention, a dockleveler is provided. The dock leveler comprises: a support structureconfigured to be mounted to a top surface of a loading dock; a deckassembly pivotally connected to the support structure, the deck assemblyhaving a top surface; and a ramp defining a transition surface betweenthe top surface of the loading dock and the deck assembly top surface,the ramp attached to the support structure and ending substantially at apivot point of the deck assembly.

In accordance with another embodiment of the present invention, a dockleveler is provided. The dock leveler comprises: means for pivotallysupporting a deck assembly configured to be mounted to a top surface ofa loading dock; a deck assembly pivotally connected to the supportingmeans; and means for providing a transition between a dock floor and thedeck assembly the transition means attached to the supporting means andconfigured to provide a transition surface generally upward inclinedfrom the dock floor to the deck assembly.

In accordance with another embodiment of the present invention, a methodof provided a bridge between a vehicle bed and a dock floor is provided.The method comprises: lowering a deck assembly from a vertical positionto a working position; and providing an upwardly inclined transitionpiece configured to aid a wheel in moving between the dock floor and thedeck assembly, wherein the transition piece and the lowered deckassembly comprise the bridge.

In accordance with another embodiment of the present invention, aplatform attachable to a loading dock is provided. The platformcomprises a plate configured to attach to a loading dock adjacent to adock face.

In accordance with another embodiment of the present invention, a systemfor reducing the likelihood of objects falling between bumpers mountedto a loading dock is provided. The system comprises: a barrier attachedto a loading dock adjacent to a vertical storing dock leveler whereinthe barrier is beneath a deck assembly portion of the dock leveler whenthe dock leveler is in a substantially horizontal position; and bumpersattached to the loading dock and located at either end of the barrier.

In accordance with another embodiment of the present invention, a systemfor reducing the likelihood of objects falling between bumpers mountedto a loading dock is provided. The system comprises: means forsupporting a dock worker attached to a loading dock adjacent to avertical storing dock leveler wherein the supporting means is beneath adeck assembly portion of the dock leveler when the dock leveler is in asubstantially horizontal position; and bumpers attached to the loadingdock and located at either end of the supporting means.

In accordance with another embodiment of the present invention, a methodof reducing the likelihood of objects falling between bumpers mounted toa loading dock is provided. The method comprises: mounting bumpers tothe loading dock; and mounting a barrier adjacent to a loading dock facebetween the bumpers.

There has thus been outlined, rather broadly, certain embodiments of theinvention in order that the detailed description thereof herein may bebetter understood, and in order that the present contribution to the artmay be better appreciated. There are, of course, additional embodimentsof the invention that will be described below and which will form thesubject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of embodiments inaddition to those described and of being practiced and carried out invarious ways. Also, it is to be understood that the phraseology andterminology employed herein, as well as the abstract, are for thepurpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view illustrating a vertically-storing, top-of-dockleveler according to a preferred embodiment of the invention in thevertically-stored position.

FIG. 2 is an exploded perspective view of the base assembly of thevertically-storing, top-of-dock leveler of FIG. 1.

FIG. 3 is a side view of the vertically-storing, top-of-dock leveler ofFIG. 1 shown in a lowered, above-dock operative position.

FIG. 4 is a is a side view of the vertically-storing, top-of-dockleveler of FIG. 1 shown in a lowered, below-dock operative position.

FIG. 5 is a side view of the vertically-storing, top-of-dock leveler ofFIG. 1 shown in a partially-lowered position with the deck assembly andthe base of the dock leveler moving away from the face of the dock.

FIG. 6 is a side view of the vertically-storing, top-of-dock leveler ofFIG. 1 shown in a lowered, operative position with the deck assembly andthe ramp moved away from the dock face for end-loading.

FIG. 7 is a side view illustrating a vertically-storing, top-of-dockleveler according to another preferred embodiment of the invention inthe vertically-stored position, with the lip extended.

FIG. 8 is a side view illustrating the vertically-storing, top-of-dockleveler of FIG. 7 in a lowered, operative position with the lipextended.

FIG. 9 is a side view illustrating the vertically-storing, top-of-dockleveler of FIG. 7 in the vertically-stored position, with the lipretracted.

FIG. 10 is a side view illustrating the vertically-storing, top-of-dockleveler of FIG. 7 in a lowered, operative position with the lipretracted.

FIG. 11 is a side view illustrating a vertically-storing, top-of-dockleveler in accordance with yet another preferred embodiment of thepresent invention in the vertically-stored position.

FIG. 12 is side view of the vertically-storing, top-of-dock leveler ofFIG. 11 in a lowered, operative position.

FIG. 13 is a side view illustrating a dock leveler incorporating acounterbalance mechanism according to a preferred embodiment of theinvention, wherein the dock leveler is lowered near the generallyhorizontal operative position.

FIG. 14 is an enlarged partial view of the counterbalance mechanism ofFIG. 13.

FIG. 15 is a side view illustrating the dock leveler of FIG. 13 in thevertical stored position.

FIG. 16 is a side view of the dock leveler of FIG. 13 in the lowestoperative position.

FIG. 17 illustrates a preliminary configuration of a tension springcounter balance mechanism with the dock leveler in a lowered workingposition.

FIG. 18 illustrates the preliminary configuration of a tension springcounter balance mechanism of FIG. 17 with the dock leveler in the storedposition.

FIG. 19 is a graphical illustration of the relative magnitude of theweight and spring rotational moments of the preliminary configuration ofa tension spring counter balance mechanism of FIG. 17 as the center ofgravity is rotated from a vertical to a horizontal position.

FIG. 20 is a graphical illustration of an exemplary net moment profilein accordance with the present invention, resulting from the weight andspring rotational moments as the center of gravity is rotated from avertical to a horizontal position.

FIG. 21 is a perspective view illustrating a vertical storing dockleveler according to a preferred embodiment of the invention, whereinthe dock leveler is lowered to the generally horizontal operative range.

FIG. 22 is a cut away side view of the dock leveler of FIG. 21, loweredto the generally horizontal operative range with the lip resting on thebed of a truck, illustrating the spring counter balance mechanism.

FIG. 23 is an enlarged partial view of the counterbalance mechanism ofFIG. 22.

FIG. 24 is an enlarged partial view of the counterbalance mechanismillustrating the dock leveler of FIG. 22 in a position slightly abovethe upper end of the designed operating range.

FIG. 25 is an enlarged partial view of the counterbalance mechanismillustrating the dock leveler of FIG. 22 in a position slightly abovethe upper end of the designed operating range with the hold down deviceengaged.

FIG. 26 is an enlarged partial view of the counterbalance mechanismillustrating the dock leveler of FIG. 22 with the hold down devicedisengaged.

FIG. 27 is a side view of the dock leveler of FIG. 22 illustrating thelifting lever in the stored lowered position and the position of thelifting lever in the raised operative position.

FIG. 28 is an enlarged partial view of the dock leveler of FIG. 22illustrating the lifting handle rotating the hold down device to adisengaged position and providing a torque enhancement relative to therotation of the dock leveler.

FIG. 29 is an enlarged partial view of the dock leveler of FIG. 22illustrating the lifting handle rotated to a position that provides adirect torque connection to the dock leveler.

FIG. 30 is an enlarged partial view of the dock leveler of FIG. 22illustrating the lifting lever with a ratchet and a pawl disengaged fromthe ratchet.

FIG. 31 is an enlarged partial view of the dock leveler of FIG. 22rotated to a position where the pawl engages a tooth on the ratchet.

FIG. 32 is a side view of the dock leveler of FIG. 21 in the storedvertical position, illustrating three positions of the lifting lever.

FIG. 33 is a side view of the dock leveler of FIG. 21 in the storedvertical position, illustrating the lip control handle with the lipextended.

FIG. 34 is a side view of the dock leveler of FIG. 21 in the storedvertical position, illustrating the lip control handle with the lipretracted.

FIG. 35 is an enlarged partial view of the lip latch mechanismillustrating the lip held extended by the lip latch.

FIG. 36 is an enlarged partial view of the lip latch mechanismillustrating the lip rotated slightly past the latched position.

FIG. 37 is an enlarged partial view of the lip illustrating the lipcontrol handle engaging the lip in a position to disengage the liplatch.

FIG. 38 an enlarged partial view of the lip illustrating the lip controlhandle engaging the lip in a position to rotate the lip to an extendedposition.

FIG. 39 is an enlarged partial view of the dock leveler in a generallyhorizontal operative position illustrating the lifting lever in thelowered position and with a second embodiment of a pawl disengaged fromthe lifting lever.

FIG. 40 is an enlarged partial view of the dock leveler in a generallyhorizontal operative position illustrating the lifting lever in apartially raised position and with a second embodiment of a pawldisengaged from the lifting lever.

FIG. 41 is view illustrating the second embodiment of the pawl.

FIG. 42 is an enlarged partial view of the dock leveler in a partiallyraised position illustrating a first tooth of the pawl engaging thelifting lever.

FIG. 43 is an enlarged partial view of the dock leveler in the verticalstored position illustrating a second tooth of the pawl engaging thelifting lever.

FIG. 44 is an enlarged partial view of the dock leveler in the verticalstored position illustrating a storage latch and release pedal.

FIG. 45 is an enlarged partial view of the dock leveler in a generallyhorizontal operative position illustrating the storage latch released.

DETAILED DESCRIPTION

The invention will now be described with reference to the drawingfigures, in which like reference numerals refer to like partsthroughout. An embodiment in accordance with the present inventionprovides a vertically-storing, top-of-dock leveler. Such devices inaccordance with some embodiments of the invention have the advantage ofbeing more economical to install and provide greater environmental andsecurity control than typical pit-style dock levelers, while also havinga greater range of operative positions than typical edge-of-dock andtop-of-dock levelers.

FIG. 1 illustrates a dock leveler 10 in accordance with one embodimentof the present invention. The dock leveler 10 includes a deck assembly12 pivotally attached to a base assembly 14 and a lock mechanism 24. Thedeck assembly 12 includes a deck plate 16 supported by side curbs 18,and a pivot shaft 20 attached to the rear end 22 (i.e. the end closestto the base assembly 14 and farthest from the vehicle bed when the deckassembly 12 is in an operative position) of the deck plate 16. The pivotshaft can be supported at each end by a roller 26 that rests on the baseassembly 14, and specifically the base plate 70 of the base assembly 14.The deck plate 16 preferably is not flat and occupies at least twoplanes. When the deck plate 16 occupies two planes, the intersection ofthe planes preferably is located near the plane of the dock face 4 whenthe deck plate 16 is in the lowered, substantially horizontal position.As shown in FIG. 3, the deck plate 16 has a first surface 15 occupying afirst plane, a second surface 17 occupying a second plane, and theintersection 19 of the first surface 15 and second surface 17 (andconsequently the intersection of the first and second planes) is locatednear the plane of the dock face 4. Such a configuration—i.e. a deckplate configured to occupy more than one plane—enables the dock levelerto achieve a lesser below dock grade as compared to conventional docklevelers having a flat deck plate occupying only a single plane,particularly when the intersection of the planes is located in the planeof the dock face or above the dock floor. A person of ordinary skillwill understand from the teachings herein that the deck plate maycomprise at least a first or second portion, which may be but are notnecessarily planar. Rather, an angle exists between the first and secondportion near the plane of the dock face thereby minimizing the gradewhen the truck is below dock. Thus, for example a first planar portionmay extend from the truck bed to a location near the dock face and thesecond portion may be a curved portion extending to the dock hinge orelse a curved portion extending to a planar portion connected to thedock hinge.

Referring back to FIG. 1, the lock mechanism 24 includes a lower link 30and an upper link 32. The lower link 30 has one end pivoting about a pin34 carried by the base assembly 14 and the other end pivoting about apin 36 attached to one end of the upper link 32. The other end of theupper link 32 pivots about a pin 38 carried by a bracket 40 attached tothe deck assembly 12. When the deck assembly 12 is in the raised (i.e.vertically-stored) position, the links 30, 32 rotate to an over-centerposition to lock the deck assembly 12 into the raised position. As shownin FIGS. 3 and 4, the links 30, 32 rotate relative to each other toallow the deck assembly 12 to lower.

The base assembly 14, shown in a detailed, exploded view in FIG. 2includes a ramp assembly 42, two spring anchor assembles 44, and twobase plate assemblies 46. The ramp assembly 42 has two side plates 48supporting an inclined ramp plate 50, and a pivot shaft engagementmechanism 52. In the illustrated embodiment, the pivot shaft engagementmechanism is a support channel and will thus be referred to as a supportchannel 52 from hereon in. The pivot shaft engagement mechanism need notbe a support channel, however; anything that positions the pivot shaft20 when the ramp assembly 42 is latched, and further allows the pivotshaft 20 to move with the ramp assembly 42 when the ramp assembly isde-latched and moved rearwardly (i.e. away from the face of the dock)can be a pivot shaft engagement mechanism.

The side plates 48 have an inside surface 56 (facing the ramp plate 50),an outside surface 58 (opposite the ramp plate 50), a forward end 54(the end nearest the dock face 4), and a rear end 60 (the end farthestfrom the dock face 4). A latch block 62 is attached to the outsidesurface 58 of each side plate 48 toward the rear end 60′ of each sideplate 48, for engagement with corresponding latch blocks 64 on the baseplate assembly 46.

The inclined ramp plate 50 extends at an upward incline from the dockfloor (not shown in FIG. 2) to the pivoting end of the deck assembly 12.The support channel 52 can be formed integrally with the ramp plate 50,or it can be a separate portion attached to the ramp plate 50. As shownin FIG. 2, the forward end 54 (i.e. the end nearest the dock face 4) ofthe ramp plate 50 rests on the support channel 52. Thus, in theillustrated embodiment, the support channel 52 is a separate portionfrom the ramp plate 50. The support channel 52 is configured to receivethe pivot shaft 20 of the deck assembly 12.

The base plate assemblies 46 each include a side plate 66 with a camslot 68. Each side plate 66 is mounted to a base plate 70 which isultimately attached to the dock floor. The side plates 66 have an insidesurface 72 (facing the ramp assembly 42), and outside surface 74(opposite the ramp assembly 42), a forward end 76 (the end nearest thedock face 4), and a rear end 78 (the end farthest the dock face 4). Alatch block 64 is attached the inside surface 72 of each base side plate66 toward the rear end 78 of each base side plate 66 for engagement withthe latch blocks 62 of the ramp assembly 42. The base plate assemblies46 also include a pivot boss 80 attached at the forward end 82 (i.e. theend nearest the dock face 4) of the base plate 70 for receiving the pin34 which attaches to the lower link 30 enabling pivoting motion.

Each spring anchor assembly 44 includes a plate assembly 94. One plateassembly 94 is mounted on each end of the pivot shaft 20, between theramp assembly 42 and base plate assembly 46. Each plate assembly 44 hasa plate 84, a support bushing 86, a pin 88, and a pin 90 carrying a camroller 92. The cam roller 92 fits within, and is positioned within, thecam slot 68. Each spring anchor assembly 44 also includes a spring 96with an upper end fastened to an adjusting bolt 98 attached to a plate100 mounted on a side curb 18 and a lower end attached to the pin 88 onthe plate assembly 94. In some embodiments, rotation of the plateassembly 94 is prevented by the cam roller 92 bearing on the cam surface102 of the base plate assembly 46. The locations of the pin 88 and theplate 84, and the rate of the spring 96 are preferably selected so thatthe deck 16 is upwardly biased when the dock leveler 10 is in the storedposition and downwardly biased when the deck assembly 12 is lowered toan operative position.

Whereas FIG. 1 illustrates the dock leveler in a stored position, FIGS.3, 4, and 6 illustrate the same dock leveler installed on the topsurface (or floor) 2 of a dock 1 with a vehicle 5 parked on the dockdriveway 3 and backed against the bumpers 108. On either side of thedock leveler 10, a bumper assembly 104 is attached to the dock face 4.The bumper assembly 104 includes a bumper bracket 106 and a resilientbumper 108. The bumpers 108 protect the dock face 4 from impact andposition the transport vehicle 5 at the desired position relative to thedock leveler 10. A shelf 105 is supported between the bumper assemblies104.

As FIGS. 1, 3, and 4 indicate, the dock leveler 10 is adapted to bridgethe gap between the loading dock 1 and the bed 6 of a transport vehicle5 parked in front of the loading dock 1. As discussed above, the dockleveler 10 includes two base plate assemblies 46 mounted on the dockfloor 2, a ramp assembly 42 resting on the dock floor 2 between the twobase plate assemblies 46, and a deck assembly 12 pivoted to the baseramp assembly 42 and base plate assemblies 46. The deck assembly 12 ismoveable between a generally vertical stored position to a lowered,generally horizontal operative position that may be upwardly inclined ordownwardly declined to provide a bridge from the dock floor 2 to atransport vehicle bed 6 that may be higher or lower than the dock floor2. FIG. 1 illustrates the dock leveler in the stored position. FIG. 3illustrates the dock leveler in a lowered, above-dock operativeposition. FIG. 4 illustrates the dock leveler in a lowered, below-dockoperative position.

FIG. 6 illustrates the dock leveler 10 in another lowered operativeposition for accommodating an end-loading condition. In normaloperation, the ramp assembly 42 is prevented from moving by the latchblocks 62 engaging the latch blocks 64 on the base plate assemblies 46.When the links 30, 32 are rotated from the locked over-center position,the deck assembly 12 can be rotated and lowered to an operative positionresting on a vehicle bed 6 as illustrated in FIGS. 3 and 4. When cargois close to the rear of the truck 5, it may interfere with the end ofthe deck assembly 12 and prevent the deck assembly 12 from resting onthe bed of the truck 6. This is known as an end-loading condition.

To allow the deck assembly 12 to be lowered for end loading, the links30, 32 remain locked in the over-center position. The rear 109 of theramp assembly 42 is raised to disengage the latch blocks 62 from thelatch blocks 64. When the deck assembly 12 is pushed rearward andpivoted toward a lowered position, the links 30, 32 cause the pivotshaft 20 and the ramp assembly 42 to move rearward. This is illustratedin FIG. 5. The rollers 26 bearing on the base plates 70 carry the weightof the deck assembly 12. The spring plate assembly 94 also movesrearward with the pivot shaft 20. The cam roller 92 moves along the camsurface 102 to maintain the angular position of the spring plateassembly 94 and thus the counterbalance force of the springs 96 is notaffected by the position of the pivot shaft 20. Preferably, when thedeck assembly 12 is lowered to an operative position, it does notprotrude beyond the front face of the bumpers 108 and end-loading can beperformed as illustrated in FIG. 6. A person of ordinary skill in theart will appreciate that although the illustrated embodiments refer tomanual mechanisms for raising and lowering the deck assembly 12, dockleveler operation can also be accomplished mechanically by means knownin the art, for example by hydraulic or electric actuating mechanisms.

When the deck assembly 12 is raised, the pivot shaft 20 moves forward tothe normal position shown in FIG. 1. The front leg 110 of the supportchannel 52 engages the pivot shaft 20 and causes the ramp assembly 42 tomove forward. When the ramp assembly 42 is fully forward the latchblocks 62 engage the latch blocks 64 on the base plate assemblies 46 andsecure the ramp assembly 42 and the pivot shaft 20 in the normalposition.

FIGS. 7-10 illustrate a dock leveler 200 according to another embodimentof the present invention.

The dock leveler 200 includes a deck assembly 212, base assembly 214,lip assembly 300, and lock mechanism 24. The deck assembly 212 issimilar to the deck assembly 12 shown in FIG. 1 and includes a deckplate 216 supported between two side curbs 218, and a pivot shaft 220attached to the rear end 222 of the deck plate 216.

The base assembly 214, similar to the base assembly 14 of FIG. 1,includes a ramp assembly 242. However, rather than having base plateassemblies configured for attachment to the top surface of a dock, theramp assembly 242 itself is configured for attachment to the top surfaceof a dock. The ramp assembly 242 has two side plates 48 supporting aninclined ramp plate 50, and a support channel 52 for receiving the pivotshaft 220. The base assembly 214 also includes a base plate 270 that isattached to the dock floor 2. A pivot boss 280 is attached at theforward end of the base plate 270 for receiving the pin 34 whichattaches to the lower link 30 of the lock mechanism 24.

In lieu of the spring anchor assembly 44 in the embodiment of FIG. 1,the dock leveler 200 has a spring 96 with an upper end fastened to anadjusting bolt 98 attached to a plate 100 mounted on a side curb 218 anda lower end attached to a pin 253 attached to the outside (i.e. the sideopposite the inclined ramp plate 50) of each side plate 48. Thelocations of the pin 253 and the plate 100 and the rate of the spring 96are selected so that the deck assembly 212 is upwardly biased when thedeck plate 216 is in the stored position and downwardly biased when thedeck plate 216 is lowered to an operative position.

The lip assembly 300 includes a lip plate 302, hinge tubes 304, a liparm 306, and counterbalancing mechanism 308. The lip assembly 300 isattached to the deck assembly 212 by a hinge pin 310. To reduce theeffort required to rotate the lip plate 302 from the retracted position(i.e. perpendicular to the deck plate 216, as shown in FIG. 9) to theextended position (i.e. parallel to the deck plate 216, as shown in FIG.7), the weight of the of the lip plate 302 is partially counterbalanced.A crank arm 312 is attached to a shaft 314 mounted on the deck assembly212. A link 316 is attached atone end to the crank arm 312 by a pin 318and at the other end to the lip arm 306 by a pin 320. A torsion spring322 biases the crank arm 312 in a clockwise direction to urge the lipplate 302 to rotate in a counterclockwise direction toward the extendedposition. A lip latch 324 has two latching surfaces 326, 328. When thelip plate 302 is rotated to the extended position, as shown in FIGS. 7and 8, the latch surface 326 engages a latch block (also referred to asa latch lug) 331 on the deck assembly 212 and prevents the lip plate 302from rotating toward the retracted position. When the lip plate 302 isretracted as shown in FIGS. 9 and 10, the latch surface 328 engages alatch block 330 on the deck assembly 212 and prevents the lip plate 302from rotating toward the extended position.

As with the embodiment of FIG. 1, in the embodiment of FIG. 7, the deckassembly 212 is moveable between a generally vertical, stored positionand a generally horizontal, operative position. The generallyhorizontal, operative position may be upwardly inclined or downwardlydeclined to provide a bridge from the dock floor to a transport vehiclethat may be higher or lower than the dock floor. FIG. 7 illustrates thedock leveler 200 in the stored position with the lip assembly 300extended. FIG. 9 illustrates the dock leveler 200 in the stored positionwith the lip assembly 300 retracted. FIG. 8 illustrates the dock levelerin the substantially horizontal, lowered operative position with the lipextended.

In normal operation, the links 30, 32 are rotated from the lockedover-center position and the deck assembly 212 is pushed forward torotate to a lowered operative position with the lip plate 302 resting onthe bed 6 of a truck 5 as shown in FIG. 8. When cargo is close to therear of the truck 5, it may interfere with the end of the lip plate 302.End-loading can be performed by releasing the lip latch 324 and rotatingthe lip plate 302 forward to the retracted position as illustrated inFIG. 9. Thus, when the deck assembly 212 is lowered the lip plate 302 isbehind the bed 6 of the truck 5 as illustrated in FIG. 10.

Thus the dock leveler of FIG. 1 and the dock leveler of FIG. 7 areexamples of embodiments of vertically-storing, top-of-dock levelersaccording to the present invention that can accommodate end loadingconditions. According to the embodiment of FIG. 1, end loading isaccommodated by shifting the pivot point of the deck assembly fartherfrom the dock face 4. Preferably the pivot point is shifted to an extentwhereby the dock leveler does not protrude past the face of the dockbumper 108. According to the embodiment of FIG. 7, the bridge betweenthe dock and the vehicle bed is effectively shortened through use of apivoting lip mechanism—the bridge is longer when the lip is extended andshorter when the lip is retracted.

FIGS. 11 and 12 illustrate a dock leveler 400 according to yet anotherembodiment of the present invention. FIG. 11 illustrates the dockleveler 400 in a vertically-stored position, attached to the dock floor2. FIG. 12 illustrates the dock leveler 400 in a substantiallyhorizontal, lowered operative position, resting on the bed 6 of avehicle 5 backed against the dock. The dock leveler 400 is a combinationof the dock levelers 10, 200 shown in FIGS. 1 and 7 in that it has thedeck assembly 12 according to FIG. 1 attached to the base assembly 214according to FIG. 7. Thus, as illustrated in FIG. 12, the operation ofthe dock leveler 400 is the similar to the normal operation of the docklevelers of FIGS. 1 and 7. Further, the dock leveler 400 is not designedto accommodate an end-loading condition because the deck assembly 12pivot axis 20 cannot shift from a first position close to the dock face4 to a second position farther from the dock face 4, and because thedeck assembly 12 does not include a lip assembly.

Other embodiments of the invention are shown in FIGS. 13-20 and will bedescribed below.

An embodiment in accordance with the present invention provides acounterbalance assembly for use with a mechanically-operated,vertically-storing dock leveler having a deck assembly connected to abase assembly at a pivot point, wherein the counterbalance assemblycomprises a spring counterbalance configured for attachment to the deckassembly of a dock leveler at one end and for attachment to the baseassembly of the dock leveler or to the dock itself at the other end. Thelongitudinal central axis of the spring defines a line of action, andthe spring is attached at both ends to the dock leveler or at one end tothe dock leveler and at the other end to the dock in such a manner thatthe position of the line of action relative to the direct line of actioncan change as the deck assembly rotates. Such a counterbalance assemblycan upwardly bias the dock leveler at certain angles of rotation,downwardly bias the dock leveler at other angles of rotation, and/orneutrally bias the dock leveler at yet other angles of rotation.

An embodiment of the present inventive counterbalance assembly 510 isshown incorporated into a vertically-storing, mechanically-operated dockleveler 512 in FIG. 13. The dock leveler 512 is shown positioned at aloading dock having a dock floor 501 and a dock face 502. The dockleveler 512 is adapted to bridge the gap between the loading dock andthe bed of a transport vehicle 506 parked in front of the loading dock.

On either side of the dock leveler 512, a bumper assembly 520 isattached to the dock face 502. The bumper assembly 520 includes a bumperbracket 522 and a resilient bumper 524. The bumper assembly 520 protectsthe dock face 502 from impact and positions the transport vehicle 506 atthe desired position relative to the dock leveler 512. A shelf 526 issupported between the bumper assemblies 520.

The dock leveler 512 includes a deck assembly 514 which is pivotallyconnected to a base assembly 516 at a pivot point 518, allowing the deckassembly 514 to rotate from a generally vertical stored position to oneor more lowered operating positions. That is, for example, the deckassembly 514 is movable between a generally vertical stored position(shown in FIG. 15) and a generally horizontal operative position thatmay be upwardly inclined (shown in FIG. 13) or downwardly declined(shown in FIG. 16) to provide a bridge from the dock floor 501 to atransport vehicle 506 that may be higher or lower than the dock floor501.

In some embodiments of the invention, the generally horizontal workingrange includes positions where an end of the deck assembly 514 is abouteight inches above horizontal to a position where the end of the deckassembly 514 is about eight inches below horizontal.

The base assembly 516 is mounted to the dock floor 501. As illustrated,the base assembly 516 includes two side plates 528 and an inclined rampplate 530. Each side plate 528 is mounted to a base plate 532 that isattached to the dock floor 501. Each side plate 528 has a bearingsurface 534 (See FIG. 14) to support the pivot shaft 536 of the deckassembly 514. The inclined ramp plate 530 extends from the dock floor501 to the pivoting end of the deck assembly 514.

The deck assembly 514 includes a deck plate 538 supported by side curbs540. A pivot shaft 536 is attached at one end of the deck plate 538 andis supported at each end by the bearing surface 534 of each side plate528. Attached to each side curb 540 is a spring anchor bracket 542.

The counterbalance assembly 510 includes a cam plate 546 and a spring548. The cam plate 546 is mounted to each base plate 532 outboard ofeach side plate 528. The cam plate has an anchor hole 550, an upper camsurface 552, and a lower cam surface 554.

The spring 548 is coupled at one end 556 to the deck assembly 514 and atthe other end 558 to the base assembly 516. The spring 548 has a centrallongitudinal axis 560 defining a line of action (also 560). The spring548 is coupled to the deck assembly 514 at a first anchor point 562 andto the base assembly 516 at a second anchor point 564. The line definedby the first and second anchor points 562, 564 is the direct line ofaction. The spring 548 is coupled to the anchor points 562, 564 in sucha manner that the position of the line of action 560 can be deflectedway from the direct line of action as the deck assembly 514 rotates fromthe vertically-stored position (shown in FIG. 15) to the one or morelowered operative positions (examples of which are shown in FIGS. 13 and16). It should be understood that although the second anchor point isshown as located on the base assembly 516, it could also be located onthe dock itself.

In the illustrated embodiment, the particular coupling is accomplishedby fixedly attaching the upper end 556 of the spring 548 to an adjustingbolt 568 attached to a spring anchor bracket 542. The lower end 558 ofthe spring 548 is flexibly attached to one end of a chain 572. The otherend of the chain 572 is attached to the anchor hole 550 in the cam plate546. Although the spring 548 is illustrated as being coupled to the baseassembly 516 by a chain 572, any flexible anchor tensile member such asa cable or a band would serve the same purpose.

As the deck assembly 514 rotates downward, the direct line of actionmoves closer to the pivot shaft 536 by virtue of the geometry of thefixed anchor points and pivot point. The interaction of the flexiblechain 572 and camming surfaces 552, 554 together operate to deflect theline of action 560 of the spring 548 away from the direct line ofaction. That is, as the deck assembly 514 rotates, the upper and lowercamming surfaces 552, 554 selectively engage the flexible chain 572shifting the location of the effective anchor point 574.

The term “effective anchor point” is the point of attachment of the endof a spring, which point's location can move as the deck assembly 514rotates. Thus, for example, in the illustrated embodiment, the“effective anchor point” is the lower end 558 of the spring 548,because, as shown in FIGS. 13-16, the location of the point 574 changesas the deck assembly 514 rotates. By contrast because the upper end 558of the spring 548 is fixedly attached to the deck assembly, that pointof attachment is termed an anchor point rather than “effective” anchorpoint. It should be noted that the “effective anchor point” may or maynot be a true anchor point, that is a point at which the spring 548 isdirectly coupled to the dock leveler 512. That is if spring end isdirectly coupled to the dock leveler 512 and that point of attachment ismoveable, it can then be an effective anchor point.

As illustrated in FIG. 13, the weight moment of the deck assembly 514 isopposed by the moment of the spring force acting at a distance b′ fromthe pivot shaft 536. The position of the anchor hole 550 (FIG. 14) inthe cam plate 546 and the rate of the spring 548 are selected to providethe desired magnitude of the counter balancing moment. As indicatedabove, as the deck assembly 514 rotates downward, the line of action 560of the spring 548 will move closer to the pivot shaft 536, and the forceof the spring 548 will increase in proportion to the deflection of thespring 548. Preferably, the position of the anchor hole 550 in the camplate 546 and the rate of the spring 548 are chosen to allow the springcounter balance moment to approximate the weight moment of the deckassembly 514. However, as the deck assembly 514 continues to rotatedownward, the distance b′ between the line of action of the spring 548and a parallel line drawn through the pivot shaft 536 decreases fasterthan the force of the spring 548 increases.

FIG. 16 illustrates the deck assembly 514 rotated to the lowestoperative position. The chain 572 is supported by the lower cam surface554 and causes the line of action of the spring force to be moved to adistance b′″ from the pivot shaft 536. The distance b′″ is greater thanthe distance from the pivot shaft 536 to a line connecting the anchorhole 550 and the spring anchor 562. Therefore the spring counter balancemoment is increased to the desired value.

Referring to FIGS. 13 and 14, as the deck assembly 514 rotates upward,the line of force of the spring 548 moves farther above the pivot shaft536 and the force of the spring 548 decreases in proportion to thedeflection of the spring 548. As the deck assembly 514 continues torotate upward, the distance b′ between the line of action 560 of thespring 548 and the pivot shaft 536 increases faster than the force ofthe spring 548 decreases. In addition the weight moment of the deckassembly 514 decreases as it moves to a more vertical position. FIG. 15illustrates the deck assembly 514 rotated to the vertical storedposition. The chain 572 is supported by the upper cam surface 552 andcauses the line of action 560 of the spring force to be moved to adistance b″ from the pivot shaft 536. The distance b″ is less than thedistance from the pivot shaft 536 to a line connecting the anchor hole550 and the spring anchor 562. Therefore the spring counter balancemoment is decreased to the desired value.

The use of cam surfaces to modify the spring counter balance momentprovides design flexibility. Not only may the spring counter balancemoment be matched to the weight moment of the deck assembly 514, butalso it may be selected to provide other features. For example, theshape of the lower cam surface 554 may be selected to provide a springcounter balance moment that is less than the weight moment when the deckassembly 514 is in the operative position so that it will rest securelyon the truck bed. The shape of the upper cam surface 552 may be selectedto provide a spring counter balance moment that is greater than theweight moment when the deck assembly 514 is above the operative positionso that it will rise easily to the stored position. Also the shape ofthe upper portion of the upper cam surface 552 may be selected so thatthe spring counter balance moment is almost equal to the weight momentwhen the deck assembly 514 is in the stored position. This will allowthe operator to easily move the deck assembly 514 to or from the storedposition.

Without being bound by theory, following is a more technical descriptionof the present invention relative to a prior art spring counter balancemechanism. FIG. 17 illustrates a preliminary configuration of a tensionspring counter balance mechanism with one end of the spring 548connected to a deck assembly 514 and the other end to base assembly 516and with the dock leveler 512 in a lowered working position. The weightof the dock leveler 512 is illustrated by arrow W acting downwardthrough the center of gravity (“CG”) of the dock leveler 512. Thedimension a′ indicates the horizontal distance from the CG to the pivotshaft 536 of the dock leveler 512. The resulting rotational moment isthe product of the weight W multiplied by the distance a′. Therotational moment of the weight of the dock leveler 512 varies from amaximum when the CG is in the horizontal plane of the pivot shaft 536 tozero when the CG is in the vertical plane of the pivot shaft 536. Themagnitude varies as the cosine of the angle of rotation of the CGmeasured from the horizontal plane.

Still referring to FIG. 17, the spring 548 is anchored to the baseassembly 516 by a pin 576 located relative to the pivot shaft 536 athorizontal and vertical dimensions of X and Y respectively. The force ofthe spring 548 is illustrated by the arrow F acting through the centerof the spring 548. The dimension b′ indicates the perpendicular distancefrom the pivot shaft 536 to the line of force of the spring 548. Therotational moment of the spring 548 acting on the dock leveler 512 isthe product of the force F multiplied by the distance b′.

FIG. 18 illustrates the preliminary configuration of the spring counterbalance mechanism with the dock leveler 512 in a vertical storedposition. As illustrated, the CG of the dock leveler 512 is almostdirectly over the pivot shaft 536 and the horizontal distance a″ fromthe CG to the pivot shaft 536 is very small. However, the distance b″from the pivot shaft 536 to the line of action of the spring force isstill large and even a small spring force will produce a significantupwardly biased spring moment.

Although the magnitude of the spring moment can be varied by changingthe spring rate, the spring tension, or the position of the anchor pin576 relative to the pivot shaft 536, the nature of the geometry is thatnone of the variables can be configured to cause the spring counterbalance moment to match the rotational moment of the weight of the dockleveler 512. Altering the parameters may change the relative shape ofthe spring moment curve relative to the weight moment curve. However,selection of parameters provides specific values only at two positionsrelative to the weight moment curve.

FIG. 19 is a graphical illustration of the relative magnitude of theweight and spring rotational moments of the preliminary configuration ofthe spring counter balance mechanism as the center of gravity is rotatedfrom a vertical to a horizontal position. As previously stated, alteringthe parameters may change the relative shape of the spring moment curverelative to the weight moment curve. However the spring moment curve isrepresentative of a preferable solution where the dock leveler 512 isbalanced to the preferable value at the horizontal position. The dockleveler 512 is slightly downwardly biased so that it remains in contactwith a transport vehicle as it moves up or down with deflection of thesuspension.

As shown in FIG. 19, the spring counter balance moment decreases as thedock leveler 512 rotates below horizontal. Thus the dock leveler 512becomes more difficult to lift as it rotates to a lower position. If thespring parameters are selected to approximate the weight balance curve,another characteristic is that the dock leveler 512 become more upwardlybiased as the dock leveler 512 rotates to the stored vertical position.This makes the dock leveler 512 difficult to lower from the storedposition. The third characteristic is that after the operator hasovercome the upward bias at the stored position, the dock leveler 512will fall all the way down until it rests on the transport vehicle.

The lower curve illustrated in FIG. 19 is the difference between theclockwise weight moment and the counterclockwise spring moment. Valuesabove the zero line represent positions of upward bias and those belowthe zero line represent positions of downward bias. Thus it is shownthat the operator must push the dock leveler 512 away from the storedposition and then it will fall all the way to the bed of the transportvehicle. Conversely, to store the dock leveler 512, the operator mustlift it almost all the way to the stored vertical position.

FIG. 20 is a graphical illustration of the relative magnitude of theweight and spring rotational moments of an embodiment according to thepresent invention. As illustrated in FIG. 13, the upward springcounterbalance moment is the product of the spring force F and thedistance b′ from the pivot shaft 536 to the line of force 560 of thespring 548. The spring parameters are preferably selected to provide thedesired counter balance force.

FIG. 15 illustrates an embodiment of the present invention with the dockleveler 512 rotated upward to the vertical stored position. The chain572 contacts the cam surface 552 and is thus deflected away from adirect line between the anchor hole 550 and the spring anchor bracket542 on the dock leveler 512. Thus the distance b″ and therefore thespring moment are reduced relative to the prior art design. Similarly,as illustrated in FIG. 16, when the dock leveler 512 is rotated downwardbelow the horizontal position, the chain 572 contacts the cam surface554 and is thus deflected above a direct line between the anchor hole550 and the spring anchor bracket 542 on the dock leveler 512. Thus thedistance b′″ and therefore the spring moment are increased relative tothe preliminary design. A person of ordinary skill will appreciate fromthe teachings herein that the shape of the cam surfaces 550, 552 can beconfigured to produce almost any desired value of spring counter balancemoment for various positions of rotation of the dock leveler 512.

A benefit of an embodiment according to this invention is illustrated bythe graph in FIG. 20. As illustrated by the right side of the graph, asthe dock leveler 512 rotates below the horizontal position, the springmoment remains a uniform amount below the weight moment. This can ensurethat the dock leveler 512 remain in contact with the bed of thetransport vehicle, yet is not more difficult to raise from a lowerposition.

As illustrated by the left side of the graph, when the dock leveler 512is rotated to the vertical stored position, the spring moment remainsslightly lower than the weight moment. This has a benefit for theoperator while raising and lowering the dock leveler 512. The springparameters and the shape of the upper cam surface 552 can be selected sothat when the dock leveler 512 is released from the stored verticalposition, it will accelerate downward until it reaches the upward biasedregion. It may then decelerate and stop before it reaches the horizontalworking position. The operator can then step on to the dock leveler 512and gently force it down onto the bed of the transport vehicle.

There is also a benefit when raising the dock leveler 512 to the storedvertical position. As described above, the weight moment preferably doesnot increase as the dock leveler rotates below the horizontal position,so that it is easer to lift. When the operator lifts the dock leveler512 above the working position, the spring moment increases beyond theweight moment so that the dock leveler 512 starts to accelerate upwardand with very little effort the operator will be able to lift it upthrough the slightly downward biased region to the stored verticalposition.

As in FIG. 19, the lower curve illustrated in FIG. 20 is the differencebetween the clockwise weight moment and the counterclockwise springmoment. Values above the zero line represent positions of upward biasand those below the zero line represent positions of downward bias. Thusit is shown that when the operator releases the dock leveler 512 fromthe stored position, it initially falls toward the bed of the transportvehicle and then decelerates when it reaches the upwardly biased region.When the operator forces the dock leveler beyond the upwardly biasedregion it falls on to the bed of the transport vehicle. Conversely tostore the dock leveler 512, the operator is required only to lift it tothe upwardly biased region and then with the assistance of the upwardbias force easily move the dock leveler 512 through the slightlydownward biased region to the stored vertical position.

Additional embodiments of the present invention are shown in FIGS. 21-38and are described below.

Another embodiment of the present invention is shown in FIG. 21 and FIG.22. The dock leveler 600 is shown positioned at a loading dock 602having a dock floor 604 and a dock face 606. The dock leveler 600bridges the gap between the loading dock 602 and the bed 608 of atransport vehicle 610 parked in front of the loading dock 602.

On either side of the dock leveler 600, a bumper assembly 612 isattached to the dock face 606. The bumper assembly 612 includes a bumperbracket 614 and a resilient bumper 616. The bumper assembly 612 protectsthe dock face 606 from impact and positions the transport vehicle 610 atthe desired position relative to the dock leveler 600.

A shelf 618 (sometimes referred to as a platform or barrier) issupported between the bumper assemblies 612. The shelf or barrier 618 isat least strong enough to support the weight of dock workers. Optionallythe shelf 618 is made of plate steel. The shelf 618 in some embodimentsof the invention has a skid resistant surface. The skid resistantsurface may be a raised cross check pattern commonly applied to platemetal or any other suitable skid resistant surface. The shelf 618 insome embodiments of the invention includes a flange (sometimes referredto as a lip) 620. Optionally, the flange 620 of the shelf 618 may extendabove the top surface of the shelf 618. (See reference numeral 27 inFIG. 3). Optionally, the barrier 618 may not be a shelf, but a net,cable system or some other suitable barrier 618 that will reduce thelikelihood of objects falling down between the bumper assemblies 612.

The shelf 618 provides a platform for dock workers to stand and accessthe bottom of the dock leveler 600. As shown in FIGS. 21 and 22 theshelf 618 falls with in the footprint made by the deck assembly 622 ofthe dock leveler 600 when the deck assembly 622 is in a substantiallyhorizontal position. According to some embodiments of the invention, thebumper assemblies 612 project farther from the dock face 606 than theshelf 612. The shelf 612 can attach to the bumper assemblies 612, to thedock floor 604, or dock face 606, or any other suitable mountingsurface.

The dock leveler 600 includes a base assembly 624, a deck assembly 622and a lip 626. As illustrated, the base assembly 624 is mounted to thedock floor 604 with bolts 628. The base assembly 624 includes two sidehousings 630 and an inclined ramp plate 632 sometimes called a pre-ramp.Each side housing 630 is mounted to a base plate 634 that is attached tothe dock floor 604 by bolts 628. A cam plate 636 and a bearing 638 aremounted to each base plate 640 within each side housing 630.

As shown in more detail in FIGS. 23 and 24, the cam plate 636 has ananchor hole 642, an upper cam surface 644, and a lower cam surface 646.A pivot shaft 648 is attached to each side housing 630. As shown inFIGS. 21 and 22, a cover assembly 650 has a cover 652 and a spring arm654. One end of the cover 652 is mounted to pivot about the pivot shaft648 attached to side housing 630. The spring arm 654 is a leaf springthat holds the cover 652 to the top of the side curb 656. The spring arm654 is welded to the top of the cover 652. As shown in FIG. 22, the endof the spring arm 654 opposite the end attached to the cover 652contacts and urges against the coil spring 658.

The deck assembly 622 includes a deck plate 660 supported by side curbs656. Attached to each side curb 656 is a spring anchor bracket 662. Apivot shaft 664 is attached at one end of the deck plate 660 and eachend of the shaft 664 is supported by a bearing 638 on each side housing630.

At the outer end of the deck assembly 622 is a lip 626 that pivots on ashaft 666. The lip 626 is normally extended to rest on the bed 608 of atruck 610 as shown in FIG. 22 but may be retracted to allow “endloading.” End loading is a condition where cargo is loaded clear to theback of the truck 610 and would interfere with the lip 626 resting onthe vehicle bed 608.

The deck assembly 622 rotates about the pivot shaft 664 from a generallyvertical stored position to one or more lowered operating positions.That is, the deck assembly 622 is movable between a generally verticalstored position (shown in FIG. 32) and a generally horizontal operativeposition (shown in FIG. 22) that may be upwardly inclined or downwardlydeclined from the generally horizontal position to provide a bridge fromthe dock floor 604 to a transport vehicle 610 that may be higher orlower than the dock floor 604. The somewhat horizontal positions a dockleveler achieves to provide a bridge between the loading dock floor 604and the vehicle bed 608, whether the vehicle bed 608 is at, above, orbelow the level of the dock floor 604 is referred to in this document asthe working range.

The weight of the deck assembly 622 and lip 626 is supported by at leastone counterbalance spring 658. The spring 658 is coupled at one end toan adjusting bolt 668 attached to the spring anchor bracket 662 on thedeck assembly 622 and at the other end to a flexible anchor member 670comprising an anchor lug 672, and pivoting links 674 and 676 (shown inFIGS. 23 and 24). The ends of the links 674 are attached to the camplate 636 by the pin 678. The configuration of the spring counterbalance components is selected so that the deck assembly 622 is downwardbiased throughout the generally horizontal working range. Having thedeck assembly 622 downwardly biased while in the working range providesthe advantage of keeping the lip 626 in contact with the vehicle 610 bed608 as the vehicle 610 and bed 608 move up and down due to the jostlingof loading and unloading.

The deck assembly 622 is upwardly biased at positions above the workingrange to assist in raising the deck assembly 622 toward the verticalstored position. The deck assembly 622 is then again downwardly biasedas it approaches the vertical stored position, changing the bias back todownwardly bias as the deck assembly 622 approaches the vertical storedposition and assists in lowering the deck assembly 622.

Factors in achieving the desired operating characteristics are the rateof the spring 658, the location of the anchor hole 642 and the shape ofthe cam surfaces 644 and 646. The cam surfaces 644 and 646 deflect theflexible anchor member 670 to vary the distance from the pivot shaft 664to the line of action of the spring 658. Moving the line of action ofthe spring 658 away from the pivot shaft 664 increases the counterbalance moment and moving the line of action of the spring 658 towardthe pivot shaft 664 decreases the counterbalance moment.

FIG. 23 illustrates the deck assembly 622 in a generally horizontaloperative position where the flexible spring anchor member 670 is incontact with the lower cam surface 646. FIG. 24 illustrates the deckassembly 622 in a relatively higher position slightly above the normaloperating range of the dock leveler 600. The flexible anchor member 670has moved away from the lower cam surface 646 and the line of action ofthe spring 658 has moved farther away from the pivot shaft 664. If thedeck assembly 622 rotates to a higher position, the line of action ofthe spring 658 will move farther away from the pivot shaft 664 and thecounter balance moment will increase to change the deck assembly 622from downwardly biased to upwardly biased and the dock leveler 600 willraise above the bed 608 of the truck 610.

FIG. 25 illustrates the dock leveler of FIG. 24 with the addition of ahold down assembly 680. The hold down assembly has a bracket 682, a pin684 and an arm 686 having locking surfaces 688 and 690. The bracket 682pivots on the pivot shaft 664 and is biased in a clockwise direction bya spring 692. The locking surface 688 has engaged the top surface of thelug 672, preventing the flexible anchor member 670 and the end of thespring 658 from moving farther away from the pivot shaft 664. Therefore,as the deck assembly 622 rotates upward, the counter balance moment willnot increase. Thus the deck assembly 622 will remain downwardly biasedand the dock leveler 600 will remain in contact with the bed 608 of thetruck 610, even if the bed 608 of the vehicle 610 moves up and down dueto jostling associated with loading and unloading the dock leveler 600.

FIG. 26 illustrates the dock leveler with the hold down assembly 680rotated counterclockwise to a position where the locking surfaces 688and 690 are disengaged from the lug 672 to allow the deck assembly 622to rotate clockwise to toward the vertically stored position.

FIG. 27 illustrates the dock leveler 600 with a lever assembly 694 toprovide the operator with a means of rotating the deck assembly 622 fromthe generally horizontal working range to a generally vertical storedposition. As shown in FIG. 28, a pin 696 is mounted to the side curb 656of the deck assembly 622. The rear edge of the side curb 656 has acontoured notch that provides stop surfaces 698 and 700. The leverassembly 694 has a plate 702 with a hole 704 that fits over the pin 696on the side curb 656 allowing the plate 702 to rotate about the pin 696.A lug 706, a tube 708 and a bar 710 are attached to the plate 702. Acontrol bar 712 is inserted in the tube 708. When the deck assembly 622is in the generally horizontal working position as shown in FIG. 27, thelever assembly 694 rotates counterclockwise to a stored position belowthe top of the side curb 656 as shown in solid lines. The lug 706contacts the stop surface 698 to prevent the lever 704 from fallingbelow the side of the curb 656.

To operate the dock leveler 600, the operator may manually lift thecontrol bar 712 to an operative position by bending down and grabbing anend of the control bar 712, or may step on the bar 710 (also shown inperspective view in FIG. 21) to rotate the plate 702 and thus thecontrol bar 712 to an operative position and then grab hold of thecontrol bar 712. The rotation of the control bar 712 by using step bar710 saves the dock worker from having to bend down to nearly groundlevel to grab the control bar 712. The operative position is shown inphantom lines in FIG. 27. When the control bar 712 is raised to theoperative position, the lever assembly 694 provides several functions.First the lug 706 contacts the pin 684 on the hold down assembly 680,causing the hold down assembly 680 to rotate counterclockwise and movethe locking surfaces 688 and 690 out of engagement with the top of thelug 672. Once the locking surfaces 688 and 690 are out of engagement,the flexible anchor member 670 is free to rise as the deck assembly 622rotates to the stored vertical position. As the hold down assembly 680rotates counterclockwise the front end of the bracket 682 contacts thebase plate 640, causing the pin 684 to have a fixed relationship to thebase assembly 624.

As the operator continues to pull on the end of the control bar 712, thelug 706 bears against the pin 684 and creates a reaction force on thepin 696 attached to the deck assembly 622 and urges the deck assembly622 to rotate clockwise toward the stored vertical position. Because thedistance from the pin 696 to the pin 684 is less than the distance fromthe pin 696 to the pivot shaft 664, the reaction force on the pin 696applies a rotational moment to the deck assembly 622 that is greaterthan the rotational moment applied by the operator to the lever assembly694. Thus the lever assembly 694 has an increased mechanical advantageover the deck assembly 622, and a force exerted by the operator on theend of the control bar 712 will cause a greater lifting moment on thedeck assembly 622 than a lever of the same length attached directly tothe deck assembly 622. This mechanical advantage reduces the forcerequired by the operator to lift the deck assembly 622 from thedownwardly biased working range. Because of the increased mechanicaladvantage, the lever assembly 694 will rotate faster than the deckassembly 622.

FIG. 29 shows the deck assembly 622 rotated above the working range andthe lever assembly 694 has rotated clockwise until the lug 706 hascontacted the stop surface 700. The lever assembly 694 is noweffectively coupled directly to the deck assembly 622. Although thelifting moment is reduced, the deck 622 is now in the upwardly biasedrange and less force is required by the operator to raise the deckassembly 622.

By limiting the increased mechanical advantage to the downwardly biasedworking range, the operator moves the lever 694 a shorter distance thanif the increased mechanical advantage had been maintained throughout thetravel. As shown in FIG. 29 the hold down assembly 680 is no longer heldin the maximum counterclockwise position, but the top of the lug 672 hasmoved above the locking surfaces 688 and 690 and the hold down assembly680 cannot impede the upward rotation of the deck assembly 622.

In some embodiments of the present invention, the lever assembly 694includes a ratchet 714 and pawl 716, as shown in FIGS. 30-31, to allowthe lever assembly 694 to engage the deck assembly 622 at intermediateangles when the deck assembly 622 is in a position above the downwardlybiased working range. The side curb 656 of the deck assembly 622 has apin 718. A pawl 716 pivots on the pin 718 and is configured so that itis maintained by gravity in a pendant position. (The position shown inFIG. 30). A ratchet plate 714 with teeth 720 is attached to the plate702 of the lever assembly 694. When the deck assembly 622 is lowered tothe working range, the pendant position of the pawl 716 is out ofengagement with the ratchet plate 714 as shown in FIG. 30.

When the operator wishes to raise the deck assembly 622 to the storedposition the pawl 716 will not prevent the lever assembly 694 fromrotating fully clockwise. This ensures that the lug 706 will contact thepin 684 on the hold down assembly 680, causing the hold down assembly todisengage from the lug 672. (See FIG. 28). The arrangement will alsoprovide an increase in mechanical advantage of the lever assembly 694over the deck assembly 622.

When the deck assembly 622 has rotated above the working range, the pawl716 engages the ratchet plate 714 as shown in FIG. 31. When rotating thedeck assembly 622 to the vertical stored position, the operator is notrequired to pull the control bar 712 to a position shown as “A” in FIG.32. Instead the operator can push the control bar 712 forward to allowthe pawl 716 to engage a different tooth 720 on the ratchet plate 714,and then pull the control bar 712 back to engage the deck assembly 622at a more convenient position shown as “B” in FIG. 32. Also, when thedeck assembly 622 is fully raised, the operator can push the control bar712 fully forward to allow the pawl 716 to engage the last tooth 720 onthe ratchet plate 714. This will hold the lever assembly 694 in a storedposition shown as “C” in FIG. 32 so that it does not fall into the pathof people or vehicles traveling past the dock leveler 600.

As shown in FIG. 33 and FIG. 34, the top surface 722 of the side curb656 of the deck assembly 622 ends short of the side surface 724 of theside curb 656 to avoid interference with the side housing 630. As shownin FIG. 21 and FIG. 22, when the deck assembly 622 is lowered to arelatively horizontal working position, there is a significant distancebetween the end of the top surface 722 of the side curb 656 and the sidehousing 630. As shown in FIG. 22, a cover assembly 650 has a cover 652and a spring arm 654. One end of the cover 652 is mounted on the pivotshaft 648 attached to side housing 630. The spring arm 654 bears againstthe spring 658 and urges the other end of the cover 652 against theunder side of the top surface 722 of the side curb 656. As shown in FIG.23 and FIG. 24, the distance between the end of the top surface 722 ofthe side curb 656 and the side housing 630 varies as the deck assembly622 rotates. Thus the end of the cover 652 will slide along the underside of the top surface 722 of the side curb 656 and cover the openingbetween the side curb 656 and the side housing 630.

FIG. 33 illustrates the dock leveler 600 with the deck assembly 622 inthe stored vertical position with the lip 626 extended. As illustratedin FIGS. 35-36 a latch bar 726 is attached to the lip 626.

In some applications it may be desirable to latch the lip 626 in theextended position. In order to accomplish this, a lip latch assembly 728(see FIG. 35) is provided on some embodiments of the invention. Thelatch assembly 728 has a lip latch 730 and a thrust bar 732. The liplatch 730 is mounted on the spring anchor bracket 662 of the deckassembly 622 and secured by the nut 734 on the adjusting bolt 668. Thetension of the spring 658 clamps the lip latch 730 to the spring anchorbracket 662. The end of the lip latch 730 engages the end of the latchbar 726 to maintain the lip 626 in the extended position. The thrust bar732 engages the edge of the spring anchor bracket 662 to resist theforce of the latch bar 726.

FIG. 36 illustrates the lip 626 rotated slightly toward the retractedposition. The end of the latch bar 726 has been forced past the end ofthe lip latch 730, causing the lip latch assembly 728 to rotate aboutthe edge of the spring anchor bracket 662 and causing the spring 658 toextend. The dimensions of the lip latch assembly 728 and the springanchor bracket 662 are selected so that the force of the spring 658 willexert sufficient force on the lip latch assembly 728 to maintain the lip628 in an extended position when the deck assembly 622 is in thegenerally horizontal working range as illustrated in FIG. 22.

Additional force acting in the direction toward the dock face 606 andparallel to a surface formed by the lip 626 in the extended position andthe deck plate on the end of the lip 626 will cause the latch bar 726 todeflect the end of the lip latch 730 or deck 660 and allow the lip 626to fall to the retracted position. This “yieldable” lip feature preventsdamage if a truck 610 should back into the lip 626 while the dockleveler 600 is left in the lowered position with the lip 626 extended.As previously described, the deflection and force of the spring 658increase when the deck assembly 622 is rotated to the generallyhorizontal working range and decrease when the deck assembly 622 isrotated to the generally vertical stored position. When the deckassembly 622 is in the stored vertical position, much less force isrequired to rotate the lip 626 from the extended, latched position andto force the latch bar 726 past the end of the lip latch 730. Inaddition to providing ease of use for the operator, using the spring 658for the lip latch 730 also reduces cost by eliminating the requirementfor an additional lip latch spring.

FIG. 33 and FIG. 34 illustrate a lip control bar 736 engaging the lip626. Preferably, the control bar 712 (also referred to as an actuator)can be removed from the lever assembly 694 and be used as control bar(also referred to as an actuator) 736 to rotate the lip 626. Asillustrated in FIG. 37 and FIG. 38 the lip 626 has an elongated hole 738and an angle 740 mounted below the bottom surface of the lip 626 whichact as a control bar receiver (also referred to as an actuatorreceiver). Other embodiments of the invention may include other types ofcontrol bar features such as tabs attached to the lip 626 or othersuitable control bar receiving arrangements. From the position of thecontrol bar 736 shown in FIG. 37, clockwise movement of the control bar736 will cause rotation of the lip 626 to the retracted position (whenthe lip 626 is in a position about perpendicular to the deck assembly622, this position may also be referred to as a pendant position). Toextend a retracted lip 626, the control bar 736 is again used.

FIG. 38 illustrates the control bar 736 engaging the lip 626 so that itcan be rotated counterclockwise toward the extended position.

The reason for the elongated hole 738 is twofold as illustrated in FIG.33 and FIG. 34. In FIG. 33 the control bar 736 is in a position thatwill easily allow the operator to lift up on the control bar 736 torotate the lip 626 and force the latch bar 726 (See FIGS. 35 and 36) outof engagement with the lip latch assembly 728. When the latch bar 726has disengaged from the lip latch 730, the lip 626 will fall by gravityto the retracted position in FIG. 34. If the hole 738 were not elongatedthen the control bar 736 would rotate to the position marked “E” andwould pull the operator forward toward the deck assembly 622. Theelongated hole 738 allows the lip 626 to retract yet allow the controlbar 736 to stop in the position marked “D” so that the operator is notrequired to reach so far forward. Similarly when the operator wishes torotate the lip 626 counterclockwise from the retracted position shown inFIG. 34 to the extended position shown in FIG. 33, the control bar 736provides the operator with more mechanical advantage in position “D”than in position “E.”

FIGS. 33 through 38 also illustrate a shock absorber 742 attached at oneend to a pin 744 on the lip 626 and at the other end to a pin 746 on thedeck assembly 622. The shock absorber 742 is configured to have littleresistance to extension and high resistance to retraction. Thus theshock absorber 742 prevents the lip 626 from dropping rapidly to theretracted position yet does not impede extension of the lip 626.

FIGS. 39 and 40 illustrates the dock leveler 600 with the deck assembly622 in a generally horizontal operative position. A latch housing 748 isfixed to the side curb 656 The latch housing 748 has a contoured shapewith stop surfaces 699 and 701, a cavity 750 and a pivot boss 752.

FIG. 41 illustrates a pawl 754 having a bearing surface 756, a firsttooth 758, a second tooth 760 and a control arm 762. As illustrated inFIGS. 39, 40, 42 and 43, the bearing surface 756 fits over the pivotboss 752 of the latch housing 748. The rotational movement of the pawl754 is limited by the clearance between the control arm 762 and theinternal cavity 750 of the latch housing 748. The pawl 754 is contouredso the center of gravity, marked CG, is forward of the pivot boss 752when the deck assembly 622 is in a lowered position as illustrated inFIGS. 39 & 40 and is rearward of the pivot boss 752 when the deckassembly 622 is in a raised position as illustrated in FIGS. 42 and 43.Thus when the deck assembly 622 is lowered, the pawl 754 rotatescounterclockwise toward the disengaged position. When the deck assembly622 is raised toward the vertical stored position the pawl 754 rotatesclockwise so that the lug 706 on the lever assembly 694 can engage oneof the teeth 758 or 760.

As illustrated in FIGS. 39 and 40, the deck assembly 622 is in agenerally horizontal operative position. In FIG. 39 the lever assembly694 is lowered to a position where the lug 706 engages the stop surface699. The pawl 754 is rotated counterclockwise so that the teeth 758 and760 are retracted into the cavity 750 and do not engage the lug 706 ofthe lever assembly 694.

In FIG. 40 the lever assembly 694 is partially raised, illustrating thatthe lever assembly 694 is free to rotate without the lug 706 engagingthe pawl 754. Thus the lever assembly 694 is free to rotate clockwise sothe lug 706 can engage the pin 684 on the hold down assembly 680 asillustrated in FIG. 28.

As illustrated in FIG. 42 the deck assembly 622 is partially raised withthe lever assembly 694 rotated forward from the initial liftingposition. The center of gravity, GC is now rearward of the pivot boss752 and the pawl 754 has rotated clockwise so that the lug 706 on thelever assembly 694 engages the first tooth 758. Thus the lever assembly694 can engage the deck assembly 622 at a more convenient position asillustrated in FIG. 42.

FIG. 43 illustrates the deck assembly 622 in the vertical storedposition with the lever assembly 694 rotated forward. The pawl 754 hasrotated farther clockwise so that the lug 706 on the lever assembly 694engages the second tooth 760 to hold the lever assembly 694 in thestored position.

According to some embodiments of the invention, a storage latch andrelease mechanism is provided. FIG. 44 is a partial cut-away viewillustrating the deck assembly 622 in the vertical stored position. Apivot shaft 764 is attached to the deck assembly 622. A latch angle(also referred to as a latch lug) 766 is attached to the inner side ofthe side housing 630 of the base assembly 624 and has a latch surface768 and a deck surface 770. A latch hook 772 has a pivot hole 774 and alatch surface 776. The latch hook 772 is mounted to rotate on the pivotshaft 764. When the deck assembly 622 is fully raised the latch surface776 of the latch hook 772 is positioned to engage the latch surface 768of the latch angle 766 and prevent the deck assembly 622 from loweringas shown with the latch hook 772 in solid lines in FIG. 44.

To lower the deck assembly 622 from the raised, stored position, arelease leveler assembly 778 is provided. The release lever assembly 778has a lever arm 780 and a foot pedal 782. The release lever assembly 778is mounted inside the side housing 630 on the pivot shaft 784. The footpedal 782 protrudes through an opening 786 in the side of the sidehousing 630. To release the latch hook 772, the operator steps on thefoot pedal 782 and causes the release lever assembly 778 to rotate tothe position illustrated by the broken lines 778 a and lift the end ofthe latch hook 772 to the position illustrated by the broken lines 772a. Thus the operator is able to disengage the latch hook 772 from thelatch angle 766 and allow the deck assembly 622 to lower to the positionshown in FIG. 45.

The latch hook 772 has a cam surface 788 that is engaged with the rampsurface 770 of the latch angle 766 when the deck assembly 622 is in thelowered position. (See FIG. 45). When the deck assembly 622 is raised,the cam surface 788 of the latch hook 772 will slide up the ramp surface770 of the latch angle 766 and achieve the latching position shown inFIG. 44.

While the embodiments shown in the accompanying FIGS. show a dockleveler to have relatively flat surfaces as the ramp deck, and lip, someembodiments of the invention may include curved surfaces. For example,in some embodiments of the invention, the deck comprises two or moresubstantially flat plates connected at an angle. This aids the dockleveler to achieve positions where the end of the deck is in a positionbelow the top surface of the loading dock. Other embodiments of theinvention, may include a deck being contoured in order to achievepositions where the end of the deck is in a below dock level position.For example, the deck may have a curved surface that will permit the endof the deck to achieve a blow dock level position. The illustrated FIGS.are meant to be exemplary. The invention is not limited to theembodiments shown and described herein.

The many features and advantages of the invention are apparent from thedetailed specification, and thus, it is intended by the appended claimsto cover all such features and advantages of the invention which fallwithin the true spirit and scope of the invention. Further, sincenumerous modifications and variations will readily occur to thoseskilled in the art, it is not desired to limit the invention to theexact construction and operation illustrated and described, andaccordingly, all suitable modifications and equivalents may be resortedto, falling within the scope of the invention.

1. A dock leveler comprising: a frame configured to be mounted to aloading dock; a deck assembly pivotally mounted to the frame; and meansfor counter balancing the deck assembly mounted at one end to the deckassembly and mounted to the frame at the other end, the counterbalancing means located substantially above the top surface of the deckassembly.
 2. The dock leveler of claim 1, wherein the counter balancingmeans runs substantially parallel along a side of the deck assembly. 3.The dock leveler of claim 1, further comprising a curb running along alength associated with the deck assembly.
 4. The dock leveler of claim3, wherein the curb provides a housing for the counter balancing means.5. The dock leveler of claim 3, wherein an end of the curb and the framedefine a gap that varies in length with respect to the position of thedeck assembly as it pivots on the frame and further comprising means forcovering configured to cover the gap.